WO2008041938A1 - Method of operating a methanol fuel cell and a methanol fuel cell with an anode catalyst comprising tellurium - Google Patents

Method of operating a methanol fuel cell and a methanol fuel cell with an anode catalyst comprising tellurium Download PDF

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Publication number
WO2008041938A1
WO2008041938A1 PCT/SE2007/050698 SE2007050698W WO2008041938A1 WO 2008041938 A1 WO2008041938 A1 WO 2008041938A1 SE 2007050698 W SE2007050698 W SE 2007050698W WO 2008041938 A1 WO2008041938 A1 WO 2008041938A1
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WO
WIPO (PCT)
Prior art keywords
fuel cell
anode
methanol
cathode
catalyst
Prior art date
Application number
PCT/SE2007/050698
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French (fr)
Inventor
Olof Dahlberg
Alf Larsson
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Morphic Technologies Aktiebolag (Publ)
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Publication date
Application filed by Morphic Technologies Aktiebolag (Publ) filed Critical Morphic Technologies Aktiebolag (Publ)
Priority to EP07835283A priority Critical patent/EP2062321A4/en
Priority to JP2009531357A priority patent/JP2010506359A/en
Publication of WO2008041938A1 publication Critical patent/WO2008041938A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9008—Organic or organo-metallic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B01J27/057—Selenium or tellurium; Compounds thereof
    • B01J27/0576—Tellurium; Compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
    • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
    • H01M8/04701—Temperature
    • H01M8/04731—Temperature of other components of a fuel cell or fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
    • H01M8/04858—Electric variables
    • H01M8/04925—Power, energy, capacity or load
    • H01M8/0494—Power, energy, capacity or load of fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
    • H01M8/1011—Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0444—Concentration; Density
    • H01M8/04447—Concentration; Density of anode reactants at the inlet or inside the fuel cell
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the fuel cell used may be a fuel cell in which, on the anode side, there is a catalyst that comprises 5 - 30% Te, preferably 5 -20% Te, and at least 40% Ag. On the cathode side of the fuel cell, there is also a catalyst.
  • the catalyst on the cathode side may comprise antraquinone or quinone.
  • the catalyst on the cathode side is embedded in phenolic resin, mainly when the cell is reversed.
  • a membrane separates the anode side from the cathode side.
  • Oxygen may be supplied to the cathode side in pure form but it is also possible to feed oxygen to the process by feeding a carrier of oxygen to the fuel cell.
  • the carrier may be ordinary air but it is deemed preferable to use hydrogen peroxide, preferably in liquid form.
  • the process may use hydrogen peroxide that is dissolved in water and has a concentration of 3 % - 30 % by weight.
  • the process may use hydrogen peroxide that is dissolved in water to a concentration of 5% by weight.
  • Electrical energy generated by the process can be used to warm liquid methanol before the methanol is fed to the anode side.
  • the methanol is then used to cool the fuel cell.
  • the temperature of the methanol will increase.
  • the methanol used in the process arrives in the fuel cell at a higher temperature, this will make the process more efficient. Using the methanol as a coolant will thus give a double advantage.
  • the reaction taking place in the fuel cell can be described in terms of a process where methanol becomes carbon dioxide, water and electrical current or CH 3 OH + H 2 O ⁇ CO 2 + 6H + + 6e ⁇ .
  • the carbon dioxide so obtained may be stored such that it can later be used in a revered process where carbon dioxide is used to produce methanol on the fuel cell (CO 2 + 6H + + 6e ⁇ ⁇ CH 3 OH + H 2 O).
  • Such a reversed process may thus comprise feeding carbon dioxide to the anode side, feeding water to the cathode side, adding an electrical current and thereby causing a reaction that, in a final stage, generates methanol.
  • a reversed process can be used in connection with such power plants where the supply of energy is not constant. This may be the case, for example, for wind power plants where it is usually not possible to predict when the wind will blow and to what extent. At times when a wind is blowing and more electricity is generated than is needed at the moment, the reversed process can be used to manufacture methanol that is stored, for example in a tank. Stored methanol may later be used to generate electricity in a fuel cell when energy from the wind is not available.
  • the method additionally comprises monitoring a variable that indicates a need for electricity and running the process to generate electricity when the monitored variable exceeds a predetermined value and reversing the process if the monitored variable lies below a predetermined value.
  • the predetermined value above which the process is run to generate electricity may be the same value which is used to determine whether the process is to be reversed. In such a case, the process is used to generate electricity when the monitored variable lies above the predetermined value and the process is revered when the monitored value does not exceed the predetermined value.
  • a first predetermined value can be used to determine if the process shall be run to generate electricity and a second predetermined value can be used to determine if the process shall be revered to generate methanol.
  • the need for electricity In periods where the need for electricity is low and electric power is available, for example electric power from a wind power plant, it may be advantageous to run the process in reverse to produce methanol. In this way, electric energy can be stored in the shape of methanol.
  • various methods may be used. For example, if the invention is applied in a limited area, the need for electricity could be determined by the judgment of a human operator or by a metering device. On a larger scale, a simple way of determining the need fro electricity may be to monitor the price of electricity. When the price of electricity is high, this indicates that the need for electricity is high. Conversely, if the price of electricity is low, this indicates that the need for electric power is low.
  • Figure 1 is a schematic representation of a fuel cell according to the invention in which the fuel cell is operated to generate electricity.
  • Figure 2 is a schematic representation of a fuel cell similar to the fuel cell of Fig. 1 but in which the process is made to run in the opposite direction to produce methanol.
  • Figure 3 is a schematic illustration of how the fuel cell may me connected to a power plant, e.g. a wind power plant.
  • the inventive method makes use of a fuel cell 1 that is schematically indicated in the Figure.
  • the fuel cell 1 has an anode 2 and a cathode 3.
  • the anode 2 is separated from the cathode 3 by a membrane 4 that functions as an electrolyte and may be of a polymer material.
  • the anode 2 has a catalyst that comprises TE (Tellurium).
  • Te represents 5% - 30% by weight of the catalyst material or 5% - 20% Te by weight.
  • other catalysts substances may be present, for example Ag (Silver).
  • Silver may constitute 40% or more by weight.
  • four openings 9, 10, 11, 12 are schematically indicated. Through these openings, fluid may enter or leave the fuel cell 1.
  • Other catalyst substances on the anode side may include Tin (Sn), gold (Au), Titanium (Ti), Titanium dioxide, Vanadium (V) and Tungsten (W).
  • a tank 6 may hold a fluid that is supplied to the anode side of the fuel cell through conduit 5 and opening 9.
  • the tank 6 may also receive fluid that exits from the cell 1 through the opening 9.
  • the catalyst on the side of the cathode 3 may comprise antraquinone or quinone and may be embedded in phenolic resin. It should be understood that the catalysts mentioned may be located on the surface of the membrane 4.
  • the methanol that is supplied to the anode side may be dissolved in water.
  • the methanol may have a concentration of 5 % - 95 % by weight, preferably 20% - 80 % and even more preferred 40% - 70%.
  • the methanol may have a concentration of 64% by weight.
  • the hydrogen peroxide may also be dissolved in water.
  • the hydrogen peroxide may be dissolved in water to have a concentration of 3 % - 10 % by weight.
  • methanol may be supplied to the anode 2 through a conduit 5 that passes around at least a part of the fuel cell 1.
  • fluid e.g. methanol
  • the fluid in conduit 5 may thus cool the fuel cell 1 by absorbing heat energy developed in the process that takes place in the fuel cell.
  • the process indicated in Fig. 1 may be operated during an extended period to generate a power output less than 20% of the maximum possible power output such that the temperature in the fuel cell 1 is kept above a predetermined level.
  • the method may additionally comprise reversing the process and feeding carbon dioxide to the side of the anode 2, feeding water to the side of the cathode 3, adding an electrical current and thereby causing a reaction that, in a final stage, generates methanol.
  • carbon dioxide is fed to the fuel cell 1 (possibly from tank 8) through opening 10 and an electrical current is added to the process through circuit 13.
  • methanol is generated.
  • FIG. 2 it is schematically indicated how methanol leaves the fuel cell 1 through opening 9. Methanol generated in such a reversed process may be stored in the tank 6 and used later to once again produce electricity. It should be noted that, in the process according to Fig. 2, electrical energy is consumed and not generated.
  • the electricity needed for the process of Fig. 2 may come from any external source. With reference to Fig. 3, it is indicated how the electricity may come from a wind power plant 7.
  • the fuel cell 1 may be used to generate electricity.
  • the fuel cell may be used to produce methanol that can later be used to produce electricity when the need for electricity is high.
  • the need for electricity may be monitored by monitoring fluctuations in the price for electricity. This may be done by, for example, a computer 14 (or other control or monitoring device) that controls the fuel cell 1 and determines whether the fuel cell 1 shall be operated to produce electricity or methanol.
  • the catalyst used on the anode side typically comprises platinum (Pt).
  • Platinum is a common suitable catalyst in fuel cells.
  • Pt can be used as a catalyst together with Ag.
  • the price of platinum is high which makes it difficult to manufacture fuel cells at a competitive price. It has now been found that Te can function as well as Pt (or almost as well as Pt) in fuel cells. The price of Te is currently such that Te can be used to manufacture fuel cells that are less expensive than fuel cells using Pt. The use of tellurium in a fuel cell can thus result in cheaper fuel cells and cheaper electricity.
  • the catalyst may comprise 60 % by weight Ag, 15 % by weight Te, 10 % by weight Au, 10 % by weight Sb and 5 % by weight Pt.
  • the catalyst may have a carrier of, for example, carbon black. If the fuel cell is to be used for making methanol, the amount of Pt may be higher but the amount of Pt should not exceed 20 % by weight of the catalyst. If the fuel cell is operated to produce methanol, the amount of Pt may be, for example, 6 - 20 % by weight of the catalyst, 8 - 20 % by weight, 10 - 20 % by weight. For example, the amount of Pt may be about 15 % by weight of the catalyst.
  • Liquid fuels also mean that the conduits for the fuel can be made smaller since the same mass occupies less space than the equivalent mass in gas form.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • Organic Chemistry (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Fuel Cell (AREA)
  • Inert Electrodes (AREA)

Abstract

The invention relates to a method of operating a fuel cell (1). The fuel cell has an anode (2) and a cathode (3). The anode (2) has a catalyst that comprises Te. The method comprises the steps of feeding methanol to the side of the anode (2) and feeding oxygen or a carrier (5) of oxygen to the cathode side (3) such that a reaction occurs that generates an electrical current. The invention also relates to a fuel cell having a catalyst that comprises Te.

Description

METHOD OF OPERATING A METHANOL FUEL CELL
AND A METHANOL FUEL CELL WITH AN ANODE CATALYST
COMPRISING TELLURIUM
FIELD OF THE INVENTION The present invention relates to a method of operating a fuel cell and to a fuel cell designed to use methanol as a fuel.
BACKGROUND OF THE INVENTION
It is known from the prior art that fuel cells can use methanol as a fuel, se for example Alexandre Hacquard; Improving and understanding Direct Methanol Fuel Cell (DMFC) performance (Thesis submitted to the faculty of Worcester Polytechnic Institute), published on http://www.wpi.cdu/Pubs/ETD/Availablc/ctd-050505- 151501/ unreslxictedΗacauardjgdf. Among the benefits of a fuel cell using methanol, one can mention that the fuel is liquid and permits a quick refuelling, that methanol can be produced at a low cost and that the fuel cell can be designed for a number of mobile and/or portable applications. Moreover, DMFC fuel cells are favourable to the environment, only water and carbon dioxide are emitted and no sulphur oxide or nitrogen oxide is formed.
It is an object of the present invention to provide an improved DMFC fuel cell and a method of operating such a cell which is cost effective and which permits a compact design.
DISCLOSURE OF THE INVENTION The invention relates to a method of operating a fuel cell, in particular a DMFC fuel cell, that has an anode and a cathode. According to the invention, methanol (methyl alcohol, CH3OH) is fed to the anode side and oxygen or a carrier of oxygen is fed to the cathode side such that a reaction occurs that generates an electrical current. According to an important aspect of the invention, the anode has a catalyst that comprises Te and the catalyst on the anode side preferably comprises 5 - 30 % Te by weight and even more preferred 5 - 20% Te by weight.
The fuel cell used may be a fuel cell in which, on the anode side, there is a catalyst that comprises 5 - 30% Te, preferably 5 -20% Te, and at least 40% Ag. On the cathode side of the fuel cell, there is also a catalyst. The catalyst on the cathode side may comprise antraquinone or quinone. In embodiments of the invention, the catalyst on the cathode side is embedded in phenolic resin, mainly when the cell is reversed. A membrane separates the anode side from the cathode side.
Oxygen may be supplied to the cathode side in pure form but it is also possible to feed oxygen to the process by feeding a carrier of oxygen to the fuel cell. The carrier may be ordinary air but it is deemed preferable to use hydrogen peroxide, preferably in liquid form. Suitably, the process may use hydrogen peroxide that is dissolved in water and has a concentration of 3 % - 30 % by weight. For example, the process may use hydrogen peroxide that is dissolved in water to a concentration of 5% by weight.
The methanol may also be dissolved in water. If methanol dissolved in water is used, the methanol may have a concentration of 5 % - 95 % by weight, preferably 20% - 80 % by weight and even more preferred 40% - 70% by weight.
Electrical energy generated by the process can be used to warm liquid methanol before the methanol is fed to the anode side. The methanol is then used to cool the fuel cell. When the methanol is used as a coolant, the temperature of the methanol will increase. When the methanol used in the process arrives in the fuel cell at a higher temperature, this will make the process more efficient. Using the methanol as a coolant will thus give a double advantage.
For the process to operate smoothly and efficiently, the temperature should not be too low. This may potentially be a problem if the process must be started from a low temperature. To counteract this possible problem, the process may be operated with a reduced output simply to keep the fuel cell at a minimum temperature (it should be remembered that the process generates heat). For example, the process may operate during an extended period to generate a power output less than 20% of the maximum possible power output such that the temperature in the fuel cell is kept above a predetermined level. Alternatively, the process could be operated to generate a power output that is no higher than 10 % of the maximum possible output or perhaps no higher than 5%.
During the reaction that takes place in the fuel cell, carbon dioxide is generated. In principle, the reaction taking place in the fuel cell can be described in terms of a process where methanol becomes carbon dioxide, water and electrical current or CH3OH + H2O → CO2 + 6H+ + 6e~. According to one embodiment of the invention, the carbon dioxide so obtained may be stored such that it can later be used in a revered process where carbon dioxide is used to produce methanol on the fuel cell (CO2 + 6H+ + 6e~ → CH3OH + H2O). Such a reversed process may thus comprise feeding carbon dioxide to the anode side, feeding water to the cathode side, adding an electrical current and thereby causing a reaction that, in a final stage, generates methanol. Such a reversed process can be used in connection with such power plants where the supply of energy is not constant. This may be the case, for example, for wind power plants where it is usually not possible to predict when the wind will blow and to what extent. At times when a wind is blowing and more electricity is generated than is needed at the moment, the reversed process can be used to manufacture methanol that is stored, for example in a tank. Stored methanol may later be used to generate electricity in a fuel cell when energy from the wind is not available.
The method additionally comprises monitoring a variable that indicates a need for electricity and running the process to generate electricity when the monitored variable exceeds a predetermined value and reversing the process if the monitored variable lies below a predetermined value. The predetermined value above which the process is run to generate electricity may be the same value which is used to determine whether the process is to be reversed. In such a case, the process is used to generate electricity when the monitored variable lies above the predetermined value and the process is revered when the monitored value does not exceed the predetermined value. As an alternative, a first predetermined value can be used to determine if the process shall be run to generate electricity and a second predetermined value can be used to determine if the process shall be revered to generate methanol. If the monitored value lies between the first and the second predetermined value, neither electricity nor methanol is generated. Over time, the need for electric power varies. For example, it is often so that the need for electricity is lower during the night and higher during the day. In countries with a cold climate, the need for electricity is often high in the winter and somewhat lower during the summer. In certain other countries with a warmer climate, it may be so that much electricity is needed during the summer to operate air conditioning equipment while the need for electricity can be lower during the winter. The process of the present invention can be run in two different directions. In one direction, the process can be used to generate electricity. In the opposite direction, electricity is used to produce methanol. In periods where the need for electricity is low and electric power is available, for example electric power from a wind power plant, it may be advantageous to run the process in reverse to produce methanol. In this way, electric energy can be stored in the shape of methanol. To determine the need for electricity, various methods may be used. For example, if the invention is applied in a limited area, the need for electricity could be determined by the judgment of a human operator or by a metering device. On a larger scale, a simple way of determining the need fro electricity may be to monitor the price of electricity. When the price of electricity is high, this indicates that the need for electricity is high. Conversely, if the price of electricity is low, this indicates that the need for electric power is low.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic representation of a fuel cell according to the invention in which the fuel cell is operated to generate electricity.
Figure 2 is a schematic representation of a fuel cell similar to the fuel cell of Fig. 1 but in which the process is made to run in the opposite direction to produce methanol.
Figure 3 is a schematic illustration of how the fuel cell may me connected to a power plant, e.g. a wind power plant.
DETAILED DESCRIPTION OF THE INVENTION
With reference to Fig.l, the inventive method makes use of a fuel cell 1 that is schematically indicated in the Figure. The fuel cell 1 has an anode 2 and a cathode 3. The anode 2 is separated from the cathode 3 by a membrane 4 that functions as an electrolyte and may be of a polymer material. The anode 2 has a catalyst that comprises TE (Tellurium). Preferably, of the catalyst substance or substances present in the anode, Te represents 5% - 30% by weight of the catalyst material or 5% - 20% Te by weight. Also other catalysts substances may be present, for example Ag (Silver). Silver may constitute 40% or more by weight. In the Figure, four openings 9, 10, 11, 12 are schematically indicated. Through these openings, fluid may enter or leave the fuel cell 1. Other catalyst substances on the anode side may include Tin (Sn), gold (Au), Titanium (Ti), Titanium dioxide, Vanadium (V) and Tungsten (W).
A tank 6 may hold a fluid that is supplied to the anode side of the fuel cell through conduit 5 and opening 9. The tank 6 may also receive fluid that exits from the cell 1 through the opening 9.
A tank 8 may hold (or receive) fluid from opening 10.
There is also a catalyst on the cathode 3 (or possibly several different catalyst substances). The catalyst on the side of the cathode 3 may comprise antraquinone or quinone and may be embedded in phenolic resin. It should be understood that the catalysts mentioned may be located on the surface of the membrane 4.
When the cell 1 is used to generate electricity, methanol (methyl alcohol) is fed to the side of the anode 2 through the opening 9. At the same time, oxygen or a carrier of oxygen is fed to the to the cathode side 3 through the opening 11. Thereby, a reaction will occur that generates an electrical current through the circuit 13. The carrier of oxygen is preferably hydrogen peroxide, and preferably in liquid form. Possibly, air could also serve as a carrier of oxygen but hydrogen peroxide (H2O2) is preferable. As a by-product on the anode side, carbon dioxide (CO2) is generated that exits through opening 10 and may (optionally) be stored in a storage tank 8 for carbon dioxide. As a by-product on the cathode side, water (H2O) is generated that leaves the fuel cell 1 through the opening 12.
The methanol that is supplied to the anode side may be dissolved in water. The methanol may have a concentration of 5 % - 95 % by weight, preferably 20% - 80 % and even more preferred 40% - 70%. For example, the methanol may have a concentration of 64% by weight. If hydrogen peroxide is used on the cathode side, the hydrogen peroxide may also be dissolved in water. Suitably, the hydrogen peroxide may be dissolved in water to have a concentration of 3 % - 10 % by weight.
As indicated in Fig. 1 , methanol may be supplied to the anode 2 through a conduit 5 that passes around at least a part of the fuel cell 1. When fluid (e.g. methanol) flows through the conduit 5, the fluid in conduit 5 may thus cool the fuel cell 1 by absorbing heat energy developed in the process that takes place in the fuel cell. This entails the further advantage that methanol that reaches the anode to take part in the reaction is warmer which makes the process more efficient.
The process indicated in Fig. 1 may be operated during an extended period to generate a power output less than 20% of the maximum possible power output such that the temperature in the fuel cell 1 is kept above a predetermined level.
With reference to Fig. 2, the method may additionally comprise reversing the process and feeding carbon dioxide to the side of the anode 2, feeding water to the side of the cathode 3, adding an electrical current and thereby causing a reaction that, in a final stage, generates methanol. As schematically indicated in Fig. 2, carbon dioxide is fed to the fuel cell 1 (possibly from tank 8) through opening 10 and an electrical current is added to the process through circuit 13. As a product of this process, methanol is generated. In Fig. 2, it is schematically indicated how methanol leaves the fuel cell 1 through opening 9. Methanol generated in such a reversed process may be stored in the tank 6 and used later to once again produce electricity. It should be noted that, in the process according to Fig. 2, electrical energy is consumed and not generated.
The electricity needed for the process of Fig. 2 may come from any external source. With reference to Fig. 3, it is indicated how the electricity may come from a wind power plant 7.
During periods when the need for electricity is high, the fuel cell 1 may be used to generate electricity. When the need for electricity is low, the fuel cell may be used to produce methanol that can later be used to produce electricity when the need for electricity is high. For example, the need for electricity may be monitored by monitoring fluctuations in the price for electricity. This may be done by, for example, a computer 14 (or other control or monitoring device) that controls the fuel cell 1 and determines whether the fuel cell 1 shall be operated to produce electricity or methanol.
In prior art prior art fuel cells for methanol, the catalyst used on the anode side (where the methanol is supplied) typically comprises platinum (Pt). Platinum is a common suitable catalyst in fuel cells. In reactions involving methanol, Pt can be used as a catalyst together with Ag. In a process where methanol is produced, it may be desirable to use an amount of Pt that is higher than in a process where methanol is consumed. The reason is that reduction of CO2 may require a higher amount of Pt. Unfortunately, the price of platinum is high which makes it difficult to manufacture fuel cells at a competitive price. It has now been found that Te can function as well as Pt (or almost as well as Pt) in fuel cells. The price of Te is currently such that Te can be used to manufacture fuel cells that are less expensive than fuel cells using Pt. The use of tellurium in a fuel cell can thus result in cheaper fuel cells and cheaper electricity.
Moreover, it has been found that, in fuel cell processes where methanol is used as a fuel, carbon monoxide is one of the by-products of the process. Carbon monoxide has a tendency to destroy the platinum catalyst. Together with platinum, carbon monoxide can also form combinations that are harmful for platinum. Tellurium has been found to resist carbon monoxide better. Therefore, the use of Te can result in a longer service life for the fuel cells 1. It should be noted that the use of Te in the catalyst does not exclude the possibility that some amount of platinum may still be used in the catalyst.
In one possible embodiment, the catalyst may comprise 60 % by weight Ag, 15 % by weight Te, 10 % by weight Au, 10 % by weight Sb and 5 % by weight Pt. The catalyst may have a carrier of, for example, carbon black. If the fuel cell is to be used for making methanol, the amount of Pt may be higher but the amount of Pt should not exceed 20 % by weight of the catalyst. If the fuel cell is operated to produce methanol, the amount of Pt may be, for example, 6 - 20 % by weight of the catalyst, 8 - 20 % by weight, 10 - 20 % by weight. For example, the amount of Pt may be about 15 % by weight of the catalyst.
If fuel in liquid form is used, this makes it easier to avoid problems with overheating. For this reason, the use of liquid fuel is preferred. Liquid fuels also mean that the conduits for the fuel can be made smaller since the same mass occupies less space than the equivalent mass in gas form.
The use of hydrogen peroxide entails the advantage that much oxygen can be supplied in a compact form. This means that smaller volumes are required.

Claims

1) A method of operating a fuel cell (1) having an anode (2) and a cathode (3), the anode (2) having a catalyst that comprises Te, preferably 5 - 30% Te by weight, and wherein the method comprises the steps of: a) feeding methanol to the side of the anode (2) and b) feeding oxygen or a carrier of oxygen to the cathode side (3) such that a reaction occurs that generates an electrical current.
2) A method according to claim 1 , wherein a carrier of oxygen is fed to the cathode side.
3) A method according to claim 2, wherein the carrier of oxygen is hydrogen peroxide, preferably in liquid form.
4) A method according to claim 2, wherein the carrier of oxygen is air.
5) A method according to claim 1, wherein the methanol is dissolved in water and has a concentration of 5 % - 95 % by weight, preferably 20% - 80 % and even more preferred 40% - 70%.
6) A method according to claim 3, wherein the hydrogen peroxide is dissolved in water and has a concentration of 3 % - 10 % by weight.
7) A method according to claim 1 , wherein the reaction generates carbon dioxide and the carbon dioxide is stored.
8) A method according to claim 5, wherein the method additionally comprises reversing the process and feeding carbon dioxide to the side of the anode (2), feeding water to the side of the cathode (3), adding an electrical current and thereby causing a reaction that, in a final stage, generates methanol.
9) A method according to claim 6, wherein the method additionally comprises monitoring a variable that indicates a need for electricity and running the process to generate electricity when the monitored variable exceeds a predetermined value and reversing the process if the monitored variable does not exceed a predetermined value. 10) A method according to claim 1, wherein electrical energy generated by the process is used to warm liquid methanol before the methanol is fed to the anode side (2).
11)A method according to claim 1, wherein the process is operated during an extended period to generate a power output less than 20% of the maximum possible power output such that the temperature in the fuel cell (1) is kept above a predetermined level.
12) A fuel cell (1) of the DMFC type designed to use methanol as fuel, the fuel cell (1) comprising an anode side with an anode (2) and a catalyst for the anode reaction, a cathode side with a cathode (3) and a catalyst for the cathode reaction, and a membrane (4) that separates the anode (2) from the cathode (3), characterised in that, on the anode side, the fuel cell (1) has a catalyst that comprises 5 -30% Te by weight and at least 40% Ag by weight.
13) A fuel cell (1) according to claim 12, wherein the catalyst on the side of the anode
(2) comprises 5 - 20% Te by weight.
14) A fuel cell (1) according to claim 12 or claim 13, wherein the catalyst on the side of the cathode (3) comprises antraquinone or quinone.
15) A fuel cell (1) according to claim 14, wherein the catalyst on the side of the cathode
(3) is embedded in phenolic resin.
PCT/SE2007/050698 2006-10-06 2007-10-02 Method of operating a methanol fuel cell and a methanol fuel cell with an anode catalyst comprising tellurium WO2008041938A1 (en)

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EP07835283A EP2062321A4 (en) 2006-10-06 2007-10-02 Method of operating a methanol fuel cell and a methanol fuel cell with an anode catalyst comprising tellurium
JP2009531357A JP2010506359A (en) 2006-10-06 2007-10-02 Method for operating a methanol fuel cell and methanol fuel cell containing tellurium in the anode catalyst

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SE0602123-2 2006-10-06
SE0602123A SE530745C2 (en) 2006-10-06 2006-10-06 Method of running a fuel cell wherein the anode has a catalyst comprising tellurium

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CN102709575A (en) * 2012-03-14 2012-10-03 温州大学 High CO-resistant anode catalyst of direct alcohol fuel cells and preparation and application

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CN1802762A (en) * 2003-07-16 2006-07-12 景垣实业株式会社 Nanostructured metal-carbon composite for fuel cell electrode catalyst and method for preparing same
GB0400166D0 (en) * 2004-01-06 2004-02-11 Ic Innovations Ltd Catalyst
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CN101589502A (en) 2009-11-25
EP2062321A4 (en) 2011-01-26
EP2062321A1 (en) 2009-05-27
JP2010506359A (en) 2010-02-25
SE530745C2 (en) 2008-09-02

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